Wireless telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as mp3 players, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing noise cancelling using a microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events.
In an adaptive noise cancellation system, it is often desirable for the system to be fully adaptive such that a maximum noise cancellation effect is provided to a user at all times. Adaptive noise cancellation systems often use a fixed feedback controller due to low cost, simplicity, wideband noise cancellation, and other advantages. However, existing feedback noise cancellation systems have disadvantages. For example, feedback noise cancellation cancels at least a portion of a source audio signal which may cause degraded audio performance of a device. In order to maintain reasonable audio performance, the gain of the feedback controller may need to be reduced, and thus noise cancellation performance is compromised. In addition, due to varying conditions (e.g., different shapes of user's ears, different ways user's wear headphones, etc.), noise cancellation strength may differ from user to user. Furthermore, a feedback controller may become unstable if a secondary path of a device utilizing ANC changes.